At first there was a high pitched whining noise from the brakes, now it is A Horrible hissing wheezing sound comes from the brake / gas pedal area. When gas is applied there is a squeaking noise and the hiss temporarily stops.
It sounds as if you have a leaking power brake booster. It uses engine vacuum to give the “power” in power brakes. Try disconnecting the vacuum hose to the booster, plug it up, and run the engine. Do not drive it this way since braking will be difficult.